Coil spring



FIG. 1 is a left front perspective view of one embodiment of a coil spring illustrating our design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right front perspective view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right side elevational view thereof;

FIG. 7 is a front view thereof; and,

FIG. 8 is a bottom view thereof. 

CLAIM The ornamental design for a coil spring, as shown and described. 